The present invention relates to a plasma processing apparatus for a semiconductor processing system, and specifically to an improvement of a window device used for leading plasma light emitted from plasma out of a process chamber. The term xe2x80x9csemiconductor processxe2x80x9d used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or an LCD substrate, by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
Conventionally, in the processes of manufacturing semiconductor devices, plasma processes, such as dry etching and plasma CVD (Chemical Vapor Deposition) are frequently utilized. A plasma processing apparatus generally used for performing such plasma processes includes an airtight process chamber in which an upper electrode and a lower electrode are disposed to face each other. According to this apparatus, a semiconductor wafer or target substrate is placed on the lower electrode, a predetermined process gas is supplied into the process chamber, and then a predetermined radio frequency (RF) power is applied to, e.g., the lower electrode. By doing so, plasma is generated in the process chamber, and is used to subject the semiconductor wafer to a predetermined plasma process.
In this kind of plasma processing apparatus, the end point of a plasma process, such as an etching process, is detected on the basis of a change in an emission spectrum of plasma excited in the process chamber, as follows. Specifically, first, the emission spectrum is transmitted from the process chamber into the light receiving portion of an end point detector disposed outside the process chamber, through a detection window for the plasma light. The detection window is made of, e.g., quartz, and formed in the sidewall of the process chamber at a position on the detection light passageway for the emission spectrum. Then, on the basis of a change in the emission spectrum thus transmitted, the end point of the etching process is detected by the end point detector.
However, during the process, adhesive matters, such as reaction products, are produced in the process chamber, and stick to the surface of the detection window inside the process chamber. As a result, transmittance of the plasma light is lowered, so the end point of the etching process becomes gradually more difficult to detect. Accordingly, the detection window requires frequent cleaning or replacement, which is problematic.
Conventionally, in order to solve this problem, there is a proposed technique in that the surface of the detection window inside the process chamber is provided with blind holes having a diameter of, e.g., about 8 mm, to enlarge the surface area of a portion near the detection window (Jpn. Pat. Appln. KOKAI Publication No. 9-330917). This technique is intended to utilize the surface area enlarged by the blind holes to decrease the amount of reaction products sticking to the detection window per unit of processing time, so that timing for cleaning or replacement of the detection window can be postponed.
However, since the detection window provided with the blind holes is made of quartz, the quartz is easily etched and dimmed by plasma and thus decreases the amount of transmitted light.
The present invention has been made in consideration of the above-described problem, and an object of the present invention is to provide a plasma processing apparatus for a semiconductor processing system in which the surface of a detection window is protected from sticking matter, such as reaction products, and is scarcely etched by plasma, so that the state of the plasma can be precisely detected for a long period of time.
According to a first aspect of the present invention, there is provided a plasma processing apparatus for a semiconductor processing system, comprising:
a process chamber enveloping a plasma generation space for generating plasma;
an exhaust mechanism configured to exhaust the process chamber and set the process chamber at a vacuum;
a process gas supply mechanism configured to supply a process gas into the process chamber;
an exciting mechanism configured to excite the process gas and turn the gas into plasma in the plasma generation space; and
a window device configured to lead plasma light emitted from the plasma out of the process chamber, wherein the window device comprises
a window plate airtightly attached to a sidewall of the process chamber and being transmissible for the plasma light,
a light guide disposed between the window plate and the plasma generation space and having a number of capillary through holes configured to guide the plasma light to the window plate, the through holes having respective inner openings facing the plasma generation space and respective outer openings facing the window plate, the light guide having a resistance against the plasma higher than the window plate and being not transmissible for the plasma light except the through holes, and
a cover plate disposed between the window plate and the light guide and covering the outer openings of the through holes, the cover plate having a resistance against the plasma higher than the window plate and being transmissible for the plasma light.
According to a second aspect of the present invention, there is provided a plasma processing apparatus for a semiconductor processing system, comprising:
a process chamber enveloping a plasma generation space for generating plasma;
an exhaust mechanism configured to exhaust the process chamber and set the process chamber at a vacuum;
a process gas supply mechanism configured to supply a process gas into the process chamber;
an exciting mechanism configured to excite the process gas and turn the gas into plasma in the plasma generation space;
a shield member detachably disposed between a sidewall of the process chamber and the plasma generation space, and configured to prevent a reaction product derived from the plasma from sticking to the sidewall; and
a window device configured to lead plasma light emitted from the plasma out of the process chamber,
wherein the window device comprises
a window plate airtightly attached to the sidewall of the process chamber and being transmissible for the plasma light,
a light guide attached to the shield member at a position between the window plate and the plasma generation space and having a number of capillary through holes configured to guide the plasma light to the window plate, the through holes having respective inner openings facing the plasma generation space and respective outer openings facing the window plate, the light guide having a resistance against the plasma higher than the window plate and being not transmissible for the plasma light except the through holes, and
a cover plate attached to the shield member at a position between the window plate and the light guide and covering the outer openings of the through holes, the cover plate having a resistance against the plasma higher than the window plate and being transmissible for the plasma light.
In a third aspect, there is provided an apparatus according to the first or second aspect, wherein the cover plate consists substantially of sapphire.
In a fourth aspect, there is provided an apparatus according to the first or second aspect, wherein the cover plate has a thickness of from 0.2 to 1 mm.
In a fifth aspect, there is provided an apparatus according to the first or second aspect, wherein the cover plate is disposed in contact with the outer openings of the through holes.
In a sixth aspect, there is provided an apparatus according to the first or second aspect, wherein the cover plate is disposed separate from the outer openings of the through holes.
In a seventh aspect, there is provided an apparatus according to the first or second aspect, wherein the through holes are oriented substantially perpendicular to a surface of the window plate.
In an eighth aspect, there is provided an apparatus according to the first or second aspect, further comprising a detector disposed outside the process chamber and configured to detect a state of the plasma based on the plasma light having passed through the window plate.
In a ninth aspect, there is provided an apparatus according to the first or second aspect, wherein the exciting mechanism comprises a pair of electrodes disposed in the process chamber and configured to form an electric field in a first direction in the plasma processing space, and a magnet disposed around the process chamber and configured to form a magnetic field in a second direction perpendicular to the first direction in the plasma generation space.